Oxygen concentrator

ABSTRACT

Branch flow channels configured respectively to supply compressed air to two sieve beds respectively are provided with air supply valves each including a diaphragm valve and an electromagnetic pilot valve for driving the diaphragm valve and configured to open and close the respective branch flow channels, a pilot flow channel configured to supply pilot air to the electromagnetic pilot valves is branched from the branch flow channels, and a check valve for preventing pilot air from flowing reversely is provided in the pilot flow channel.

TECHNICAL FIELD

The present invention relates for example to an oxygen concentratorconfigured to be used in an at home oxygen therapy that a patient havinga respiratory disorder performs an oxygen inhalation at home, andgenerate and output oxygen at a high concentration from air in theatmosphere.

BACKGROUND ART

As an oxygen concentrator of this type, as disclosed in PatentLiterature 1 for example, a configuration of a PSA (Pressure SwingAdsorption) system using an absorbing material (zeolite) havingproperties such as selectively adsorbing nitrogen under increasedpressure and discharging the adsorbed nitrogen under reduced pressure isknown, and this system is also referred to as an adsorption system.

The oxygen concentrator having the adsorption system as described aboveis, as illustrated in FIG. 10 includes two sieve beds Ta, Tb filled withthe absorbing material (zeolite) configured to adsorb nitrogen, acompressor C configured to supply compressed air to these sieve beds Ta,Tb, respective branch flow channels Fa, Fb configured to constitute partof air supply flow channel for supplying the compressed air from thecompressor C to the two sieve beds Ta, Tb, respective air supply valvesPVa, PVb configured to open and close the branch flow channels Fa, Fbindependently, respective air exhaust flow channels Ea, Eb configured toopen the respective sieve beds Ta, Tb to the atmosphere, and respectiveair exhaust valves EVa, EVb configured to open and close the exhaustflow channels Ea, Eb independently.

The air supply valve PVa of the branch flow channel Fa continuing to oneTa of the two sieve beds is opened and the exhaust valve EVa of theexhaust flow channel Ea is closed, and simultaneously, the air supplyvalve PVb of the branch flow channel Fb continuing to the other Tb isclosed and the exhaust valve EVb of the exhaust flow channel Eb isopened, so that oxygen at a high concentration can be obtained bysupplying the compressed air to the one sieve bed Ta. In the meantime,since the other sieve bed Tb is decompressed, and hence nitrogenadsorbed to the zeolite is separated and discharged to the atmosphere.In addition, the air supply valves PVa, PVb and the exhaust valves EVa,EVb are switched into an inverted opening-and-closing pattern, so thatoxygen at a high concentration can be obtained by supplying thecompressed air to the other sieve bed Tb and, in the meantime, nitrogenadsorbed to zeolite of the one sieve bed Ta is separated and dischargedto the atmosphere.

In other words, by switching the opening-and-closing pattern of therespective air supply valves PVa, PVb and the exhaust valves EVa, EVbalternately, the oxygen at a high concentration can be continuouslyobtained through the respective sieve beds Ta, Tb.

Now, as the air supply valves PVa, PVb and the exhaust valves EVa, EVb,a configuration in which a normally open electromagnetic pilot valve 20is assembled to a diaphragm valve 10 as illustrated in FIG. 2 isconceivable, and is configured in such a manner that when theelectromagnetic pilot valve 20 is OFF, pilot air is supplied to thediaphragm valve 10 via a pilot flow channel Fp branched from the airsupply flow channel and the branch flow channels Fa, Fb and the exhaustflow channels Ea, Eb are closed and, in contrast, when theelectromagnetic pilot valve 20 is ON, supply of pilot air to thediaphragm valve 10 is blocked and, in contrast, the branch flow channelsFa, Fb and the exhaust flow channels Ea, Eb are opened.

In this manner, in the case where the pilot flow channel Fp configuredto supply the pilot air to the electromagnetic pilot valve 20 isbranched from the air supply flow channel, immediately after theopening-and-closing pattern of the respective air supply valves PVa, PVband the exhaust valves EVa, EVb is switched and the sieve bed configuredto generate oxygen is switched from the one Ta to the other Tb, theother sieve bed Tb is in a state in which the pressure is still low dueto the decompression until a moment immediately before, the pressure ofthe compressed air supplied from the compressor C drops temporarily asillustrated in FIG. 11, and simultaneously, the pilot pressure alsodrops.

On the other hand, the air supply valve PVa of the one sieve bed Ta,which is on the exhaust side, is to be supplied with pilot air andclosed normally. However, since the residual pressure in the sieve bedTa is still in a high state, the diaphragm valve 10 of the air supplyvalve PVa is opened because the pressures applied to both surfaces of adiaphragm 13 thereof are off-balanced (see hatched portion in FIG. 11)by dropping of the pilot pressure as described above and, consequently,exhaust air containing nitrogen at a high concentration flowstemporarily reversely through the air supply flow channel and flowsdisadvantageously into the other sieve bed Tb, which is on the sidewhere oxygen is generated. The problem as described above occurs alsoimmediately after switching of the sieve bed configured to generateoxygen from the other Tb to one Ta (see dot portion in FIG. 11). In FIG.11, vertical dot lines indicate timing of turning ON and OFF alternatelyof a distribution of power to the electromagnetic pilot valves 20 of therespective air supply valves PVa, PVb, that is, timing of switching ofthe opening-and-closing pattern of the respective air supply valves PVa,PVb and the respective exhaust valves EVa, EVb.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No.2013-132359

SUMMARY OF INVENTION Technical Problem

A technical problem of the present invention is to prevent exhaust airof a sieve bed on an air exhaust side from flowing reversely in an airsupply flow channel of compressed air and flowing into a sieve bed on aside where oxygen is generated immediately after switching of the sievebed which is in charge of supplying the compressed air in an oxygenconcentrator configured to be capable of switching the sieve bed to besupplied with the compressed air between the two sieve beds alternatelyso as to be capable of generating oxygen at a high concentrationcontinuously.

Solution to Problem

In order to solve the technical problem, there is provided an oxygenconcentrator of the present invention including: a compressed air supplysource configured to output compressed air; first and second sieve bedsincluding an absorbing material configured to selectively adsorbnitrogen from air under increased pressure and discharge the adsorbednitrogen under reduced pressure integrated therein and configured togenerate oxygen at a high concentration by separating nitrogen from thecompressed air; an air supply flow channel configured to supply thecompressed air from the compressed air supply source to the respectivesieve beds respectively; and an exhaust flow channel configured todischarge exhaust air in each of the sieve beds to the atmosphererespectively, the air supply flow channel including a main flow channelconnected to the compressed air supply source and first and secondbranch flow channels branched from the main flow channel and connectedto the first and second sieve beds, first and second air supply valvesprovided in the first and second branch flow channels and configured tocommunicate the compressed air supply source with the first and secondsieve beds alternately; an exhaust valve provided in the exhaust flowchannel and configured to communicate the first sieve bed with theatmosphere when the first air supply valve is closed, and communicatethe second sieve bed with the atmosphere when the second air supplyvalve is closed, wherein the air supply valves each including adiaphragm valve as a main valve and an electromagnetic pilot valveconfigured to drive the main valve in a direction of closing the branchflow channel by pilot air, a pilot flow channel configured to supply thepilot air to the electromagnetic pilot valves is branched from aposition on the upstream side of the air supply valves in the air supplyflow channel, and a check valve configured to prevent the pilot air fromflowing reversely is provided in the pilot flow channel.

At this time, one pilot flow channel configured to supply the pilot airto both of the electromagnetic pilot valves of the first and second airsupply valves may be branched from the air supply flow channel, oralternatively, first and second pilot flow channels configured to supplythe pilot air to the respective electromagnetic pilot valves of thefirst and second air supply valves may be branched from the air supplyflow channel respectively.

Furthermore, in a preferred embodiment of the oxygen concentrator of theinvention, the first and second air supply valves and the exhaust valveare mounted on a single manifold base, the manifold base includes theair supply flow channel, the pilot flow channel branched therefrom, andthe exhaust flow channel formed therein, and the check valve mountedtherein, the manifold base is provided with a check valve mounting holefor inserting and mounting the check valve from the outside formedtherein, the pilot flow channel is formed by a primary-side flow channelhole extending from a side wall of the check valve mounting hole to theair supply flow channel and a secondary-side flow channel hole extendingfrom an inner portion of the check valve mounting hole to theelectromagnetic pilot valve, the check valve includes a hollow outercylinder provided with a first opening configured to communicate withthe secondary-side flow channel hole at an end in an axial direction,and is fitted in the check valve mounting hole with the first opening onthe inner side, and a check valve main body configured to prevent pilotair from a hollow core cylinder disposed in the outer cylinder and thesecondary-side flow channel hole from flowing reversely, the pilot airfrom the primary-side flow channel hole is introduced into the corecylinder through first and second air introducing holes opened in sidewalls of the outer cylinder and the core cylinder, is introduced outfrom the interior of the core cylinder through an air deriving holeopened in the core cylinder, and is guided to the first opening via aperiphery of the check valve main body.

Accordingly, the check valve can be mounted easily in the pilot flowchannel formed in the interior of the manifold base from the outside ofthe manifold base.

At this time, the check valve main body may be an annular lip sealhaving a cross sectional shape of a V-shape opening on the first openingside of the outer cylinder or, alternatively, the air deriving hole maybe formed in an end surface of the core cylinder located at the positionon the first opening side of the outer cylinder and may be formed sothat a poppet valve as the check valve main body provided in the outercylinder comes into and out of contact with a valve seat formed so as tosurround the air deriving hole. An air filter is preferably mounted inthe core cylinder so as to cover the second air introducing holes.

In a more preferable embodiment of the oxygen concentrator of thepresent invention, a second opening is formed at the other end, which ison a side opposite to the first opening of the outer cylinder so thatthe core cylinder can be fit in the outer cylinder through the secondopening, and the check valve mounting hole is hermetically closed by asealing cap configured to close the second opening of the outercylinder.

Advantageous Effects of the Invention

In the oxygen concentrator of the present invention, the first andsecond air supply valves for supplying compressed air alternately to thefirst and second sieve beds are provided in the air supply flow channelconnected to the compressed air supply source, and the pilot flowchannel configured to supply the pilot air to the electromagnetic pilotvalve of the air supply valve is branched from a position on theupstream side of the air supply valve in the air supply flow channel,and the check valve configured to prevent the pilot air from flowingreversely is provided in the pilot flow channel. Therefore, even thoughthe pressure of supplied compressed air is dropped temporarilyimmediately after the sieve bed configured to supply the compressed airand generate oxygen at a high concentration is switched from one to theother, the pilot pressure is prevented from dropping in the same manner,so that the required pilot pressure can be maintained. Consequently, theair supply valve connected to the sieve bed on the air exhaust side (theside of being regenerated) and configured to be closed normally can beprevented from opening and thereby causing exhaust air in the sieve bedto flow reversely in the air supply flow channel and flow into the sievebed on the side in which the oxygen at a high concentration isgenerated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic fluid circuit drawing illustrating one embodimentof an oxygen concentrator according to the present invention.

FIG. 2 is a cross-sectional view illustrating structure of an air supplyvalve and an exhaust valve in FIG. 1.

FIG. 3 is a schematic graph illustrating pressure variations in thefluid circuit in FIG. 1.

FIG. 4A is a plan view illustrating a state in which the respective airsupply valves and the respective exhaust valves are mounted on amanifold base.

FIG. 4B is a front view illustrating a state in which the respective airsupply valves and the respective exhaust valves are mounted on amanifold base.

FIG. 4C is a side view illustrating a state in which the respective airsupply valves and the respective exhaust valves are mounted on amanifold base.

FIG. 5 is a perspective view illustrating an appearance of the manifoldbase, an appearance and a method of mounting a pilot check valve.

FIG. 6 is an enlarged cross-sectional view of a principal portion of astate in which the pilot check valve is mounted on the manifold base.

FIG. 7 is an exploded perspective view of the pilot check valve.

FIG. 8 is an enlarged cross-sectional view of a principal portion of amodification of the pilot check valve.

FIG. 9 is a schematic fluid circuit drawing of an oxygen generatingportion illustrating another embodiment of an oxygen concentratoraccording to the present invention.

FIG. 10 is a schematic fluid circuit drawing illustrating a generaloxygen concentrator.

FIG. 11 is a schematic graph illustrating pressure variations in thefluid circuit in FIG. 10.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of an oxygen concentrator of the presentinvention will be described in detail with reference to the drawings.

An oxygen concentrator 1 is configured to generate and output oxygen ata high concentration from air in the atmosphere by using an absorbingmaterial having properties such as selectively adsorbing nitrogen fromair in the atmosphere under increased pressure and discharging theadsorbed nitrogen under reduced pressure, is referred to as PSA(Pressure Swing Adsorption) system, and is used in an at home oxygentherapy that a patient having a respiratory disorder performs an oxygeninhalation at home, for example.

As illustrated in FIG. 1, the oxygen concentrator 1 roughly includes anoxygen generating portion 2 configured to generate oxygen at a highconcentration from the atmosphere, and an oxygen supply portion 50configured to supply the oxygen at a high concentration generated in theoxygen generating portion 2 to an output instrument 51 such as acannula.

The oxygen generating portion 2 includes a compressor 3 as a compressedair supply source configured to compress and output air in theatmosphere, first and second sieve beds 4A, 4B having zeolite as theabsorbing material integrated therein and configured to selectivelyseparate nitrogen from the compressed air output from the compressor 3and generate oxygen at a high concentration, an air supply flow channel5 disposed between the compressor 3 and the respective sieve beds 4A, 4Band configured to supply the compressed air respectively to the sievebeds 4A, 4B, and an exhaust flow channel 6 configured to dischargeexhaust air from the respective sieve beds 4A, 4B to the atmosphererespectively.

The air supply flow channel 5 includes a main flow channel 5 c connectedto the compressor 3 at one end thereof and first and second branch flowchannels 5 a, 5 b branched at the other end of the main flow channel 5 cand connected to the first and second sieve beds 4A, 4B. At a midsectionof the first and second branch flow channels 5 a, 5 b, first and secondair supply valves 7 a, 7 b configured to communicate the compressor 3with the first and second sieve beds 4A, 4B alternately by opening andclosing the branch flow channels 5 a, 5 b alternately are provided,respectively.

The exhaust flow channel 6 is formed by first and second exhaust flowchannels 6 a, 6 b in which exhaust air from the first and second sievebeds 4A, 4B passes respectively. A first exhaust valve 8 a configured toopen when the first air supply valve 7 a is closed to communicate thefirst sieve bed 4A with the atmosphere and discharge exhaust air in thefirst sieve bed 4A to the atmosphere is provided in the first exhaustflow channel 6 a, and a second exhaust valve 8 b configured to open whenthe second air supply valve 7 b is closed to communicate the secondsieve bed 4B with the atmosphere and discharge exhaust air in the sievebed 4B to the atmosphere is provided in the second exhaust valve 6 b.

Here, a single pilot flow channel 9 configured to supply pilot air torespective electromagnetic pilot valves 20 of the first and second airsupply valves 7 a, 7 b and the first and second exhaust valves 8 a, 8 bdescribed later in detail is branched from a position on the upstreamside of the second air supply valve 7 b in the second branch flowchannel 5 b.

The respective electromagnetic pilot valves 20 are respectivelyconnected to a control unit 60 as illustrated in FIG. 2, so that therespective valves 7 a, 7 b, 8 a, 8 b can be operated to open and closeby the control unit 60.

In other words, in the oxygen concentrator 1, a “first valveopening-and-closing pattern” in which the first air supply valve 7 a andthe second exhaust valve 8 b are opened and the second air supply valve7 b and the first exhaust valve 8 a are closed to supply compressed airto the first sieve bed 4A to generate oxygen at a high concentrationand, at the same time, exhaust air containing nitrogen at a highconcentration in the second sieve bed 4B is discharged to the atmosphereto re-generate the sieve bed 4B, and a “second valve opening-and-closingpattern” in which the second air supply valve 7 b and the first exhaustvalve 8 a are opened and the first air supply valve 7 a and the secondexhaust valve 8 b are closed to supply compressed air to the secondsieve bed 4B to generate oxygen at a high concentration and exhaust aircontaining nitrogen at a high concentration in the first sieve bed 4A isdischarged to the atmosphere to re-generate the sieve bed 4A areswitched alternately by the control unit 60, so that the oxygen at ahigh concentration can be generated continuously.

In contrast, the oxygen supply portion 50 is configured to store theoxygen at a high concentration generated in the respective sieve beds4A, 4B of the oxygen generating portion 2 once in a tank 52, and outputthe oxygen at a high concentration to the output instrument 51, andincludes first and second output flow channels 53 a, 53 b configured tooutput the oxygen at a high concentration from the first and secondsieve beds 4A, 4B respectively and a third output flow channel 53 cconnected to the output instrument 51 via the tank 52 after havingjoined the first and second output flow channels 53 a, 53 b. Here, thefirst and second output flow channels 53 a, 53 b are provided withoutput-side check valves 54 a, 54 b for preventing the oxygen at a highconcentration from flowing reversely from the tank 52 to the respectivesieve beds 4A, 4B.

Then, the oxygen at a high concentration stored in the tank 52 isintroduced to the output instrument 51 via a decompression valve 55, aflow rate regulation valve 56, a filter 57, and a moisturizer 58provided in the third output flow channel 53 c. Here, since the zeolitefilled in the sieve beds 4A, 4B has a property to adsorb not onlynitrogen in the air but also water content and hence the oxygen at ahigh concentration is output from the sieve beds 4A, 4B in an extremelydry state, the moisturizer 58 has a role to moisturize the oxygen at ahigh concentration.

In order to improve re-generation efficiency of the pair of sieve beds4A, 4B and generation efficiency of the oxygen at a high concentration,the first output flow channel 53 a and the second output flow channel 53b may be connected with a conduit provided with an orifice or a conduitprovided with a pressure equalizing valve on the upstream side of theoutput-side check valves 54 a, 54 b.

Subsequently, configurations of the air supply valves 7 a, 7 b and theexhaust valves 8 a, 8 b will be described further in detail. The firstand second air supply valves 7 a, 7 b each include a diaphragm valve 10as a main valve configured to open and close the branch flow channels 5a, 5 b of the air supply flow channel 5, and the electromagnetic pilotvalve 20 configured to drive the diaphragm valve 10 in the direction ofclosing the branch flow channels 5 a, 5 b by pilot air introducedthrough the pilot flow channel 9 as illustrated in FIG. 1 and FIG. 2.

The diaphragm valve 10 includes a casing 11 including a first portion 11a and a second portion 11 b divided into upper and lower portions andconfigured to form a space 12 in the interior thereof, and a diaphragm13 formed of an elastic material such as rubber into a disc shape, heldbetween the first portion 11 a and the second portion 11 b of the casing11 at a peripheral edge portion 13 c thereof and disposed in the space12 at a body portion 13 d on the inner side thereof. The space 12 ishermetically divided into a first drive chamber 12 a formed on a firstpressure receiving surface 13 a side (lower surface side in the drawing)of the diaphragm 13, which is one of the surfaces, and a second drivechamber 12 b formed on a second pressure receiving surface 13 b side(upper surface side in the drawing) thereof, which is the other surface,by the diaphragm 13.

The casing 11 is provided with first port 14 a to which the branch flowchannels 5 a, 5 b on the compressor 3 side are connected, a second port14 b to which the branch flow channels 5 a, 5 b on the sieve beds 4A, 4Bside are connected, a third port 14 c to which the pilot flow channel 9is connected, and a forth port 14 d opening to the atmosphere fordischarging exhaust air of the electromagnetic pilot valves 20 on abottom surface thereof. The first and second ports 14 a, 14 bcommunicate with the first drive chamber 12 a, and a valve seat 15 isformed on an inner surface of the space 12 in the periphery of thesecond port 14 b so as to surround the second port 14 b.

The diaphragm 13 is provided with a sealing rib 13 e configured to comeinto and out of contact with the valve seat 15 to isolate or communicatethe connecting between the first port 14 a and the second port 14 bformed into an annular shape on the first pressure receiving surface 13a. The body portion 13 d of the diaphragm 13 moves in the space 12toward the second drive chamber 12 b only when a pressure acting on thefirst pressure receiving surface 13 a of the diaphragm 13 becomes largerthan a pressure acting on the second pressure receiving surface 13 b bya predetermined amount ΔP and, consequently, the sealing rib 13 e movesaway from the valve seat 15 so that the first port 14 a and the secondport 14 b communicate with each other.

In each of the air supply valves 7 a, 7 b of this embodiment, a metallicfirst spring seat 17 having a hollow projecting portion 17 a and aflange portion 17 b formed in the periphery thereof and having adiameter slightly larger than that of the sealing rib 13 e is mounted ata center portion of the second pressure receiving surface 13 b of thediaphragm 13 so that the flange portion 17 b is embedded into thediaphragm 13. The interior of the projecting portion 17 a of the springseat 17 is filled with an elastic material which forms the diaphragm 13.In contrast, a second spring seat 18 having a depressed shape is formedso as to oppose the first spring seat 17 on an inner surface opposingthe second pressure receiving surface 13 b of the second drive chamber12 b, and a coil spring 16 as a biasing member configured to bias thebody portion 13 d of the diaphragm 13 toward the first drive chamber 12a is provided between the first and second spring seats.

Accordingly, the value of ΔP required for opening the diaphragm valve 10is set to be larger value. A plurality of projections 13 f arrayed in anannular shape having substantially the same diameter as the diameter ofthe sealing rib 13 e are formed in the periphery of the first springseat 17 on the second pressure receiving surface 13 b of the diaphragm13 so as to come into abutment with the inner surface of the seconddrive chamber 12 b opposing the second pressure receiving surface 13 bwhen the diaphragm valve 10 is in a fully open state to prevent thesecond pressure receiving surface 13 b from coming into tight contactwith the inner surface.

The electromagnetic pilot valve 20 includes a cylindrical solenoid 21, apower supply terminal 22 connected to the control unit 60 and configuredto distribute power to the solenoid 21, a fixed iron core 23 disposed inthe solenoid 21, a movable iron core 24 disposed in the solenoid 21coaxially with the fixed iron core 23, and a valve portion 25 operatedby the movement of the movable iron core 24 in the axial direction. Apilot supply channel 10 a configured to introduce the pilot air from thethird port 14 c to which the pilot flow channel 9 is connected to thevalve portion 25 of the pilot valve 20, a pilot supply-and-exhaustchannel 10 b configured to connect the valve portion 25 to the seconddrive chamber 12 b of the diaphragm valve 10 and supply and dischargethe pilot air to the second drive chamber 12 b, and a pilot exhaustchannel 10 c configured to communicate the valve portion 25 to theatmosphere and exhaust the pilot air introduced out from the seconddrive chamber 12 b to the valve portion 25 through the pilotsupply-and-exhaust channel 10 b to the atmosphere through the forth port14 d are formed in the interior of the casing 11 of the diaphragm valve10.

When the power is not distributed to the solenoid 21 (at the time ofOFF), the movable iron core 24 is separated from the fixed iron core 23by a biasing force of a spring 26, the pilot supply channel 10 a and thepilot supply-and-exhaust channel 10 b are brought into communicationwith each other by the valve portion 25, so that the pilot air isintroduced from the pilot flow channel 9 to the second drive chamber 12b of the diaphragm valve 10. Accordingly, the body portion 13 d of thediaphragm 13 moves toward the first drive chamber 12 a against thepressure acting on the first pressure receiving surface 13 a, and thesealing rib 13 e is pressed against the valve seat 15 so that the branchflow channels 5 a, 5 b are closed.

In contrast, when the power is distributed to the solenoid 21 (at thetime of ON), the movable iron core 24 is adsorbed by the fixed iron core23, the pilot supply-and-exhaust channel 10 b and the pilot exhaustchannel 10 c are brought into communication with each other by the valveportion 25, so that the pilot air is discharged from the second drivechamber 12 b to the atmosphere. Accordingly, the body portion 13 d ofthe diaphragm 13 moves toward the second drive chamber 12 b against abiasing force of the coil spring 16 acting on the second pressurereceiving surface 13 b, so that the sealing rib 13 e moves away from thevalve seat 15 so that the branch flow channels 5 a, 5 b are opened.

In other words, the electromagnetic pilot valve 20 is a normally opensolenoid valve, and is configured in such a manner that the branch flowchannels 5 a, 5 b are closed by the diaphragm valve 10 to block thesupply of the compressed air to the sieve beds 4A, 4B at the time whenthe power is not distributed (at the time of OFF), and the branch flowchannels 5 a, 5 b are opened by the diaphragm valve 10 to allow thecompressed air to be supplied to the sieve beds 4A, 4B at the time whenthe power is distributed (at the time of ON).

The exhaust valves 8 a, 8 b may basically have the same structure as theair supply valves 7 a, 7 b illustrated in FIG. 2. However, in thisembodiment, the coil spring 16 is omitted as illustrated in FIG. 1 aswell.

When the power is not distributed to the electromagnetic pilot valve 20,the exhaust flow channels 6 a, 6 b are closed by the diaphragm valve 10,and hence the sieve beds 4A, 4B are isolated from the atmosphere, andwhen the power is distributed, the exhaust flow channels 6 a, 6 b areopened by the diaphragm valve 10 so that exhaust air from the sieve beds4A, 4B is discharged to the atmosphere.

In the case where the air supply valves 7 a, 7 b of the diaphragm typeas described above are used, when the sieve bed in charge of generatingoxygen is switched from the first sieve bed 4A to the second sieve bed4B, for example, that is, when the pattern is switched from the “firstvalve opening-and-closing pattern” to the “second valveopening-and-closing pattern”, the second sieve bed 4B is in a state inwhich internal pressure is still lower at the moment immediately afterby the exhaust air until immediately before. Therefore, the pressure ofthe compressed air to be supplied from the compressor 3 through the airsupply flow channel 5 drops temporarily as illustrated in FIG. 11. Incontrast, at that time, internal pressure of the first sieve bed 4A isstill in a high state by the air supply until immediate before.

If the pilot pressure supplied to the electromagnetic pilot valve 20drops simultaneously through the pilot flow channel 9 branched from theair supply flow channel 5, a high internal pressure of the first sievebed 4A is applied to the first drive chamber 12 a of the diaphragm valve10 of the first air supply valve 7 a through the second port 14 b, andthe dropped pilot pressure is applied to the second drive chamber 12 bthrough the third port 14 c.

Then, although the diaphragm valve 10 of the first air supply valve 7 ais normally to be closed by a supply of the pilot air, the diaphragmvalve 10 is opened by an amount more than the value of ΔP required foropening the diaphragm valve 10 (see hatched portion in FIG. 11) from thereasons described above and, consequently, exhaust air from the firstsieve bed 4A containing nitrogen at a high concentration flowstemporarily reversely in the air supply flow channel 5 and flows intothe second sieve bed 4B, which is a side where oxygen is generated.

Such a problem also occurs when the sieve bed in charge of generatingoxygen is switched from the second sieve bed 4B to the first sieve bed4A, that is, immediately after switching from the “second valveopening-and-closing pattern” to the “first valve opening-and-closingpattern” (See dot portion in FIG. 11).

Therefore, in this embodiment, as illustrated in FIG. 1, a pilot checkvalve 40 for maintaining the pilot pressure by preventing the pilot airfrom flowing reversely from the electromagnetic pilot valve 20 sidetoward the air supply flow channel 5 is provided at a position of theupstream side of the electromagnetic pilot valves 20 of the respectiveair supply valves 7 a, 7 b in the pilot flow channel 9 (that is, the airsupply flow channel 5 side). Accordingly, as illustrated in FIG. 3, eventhough the air supply pressure drops, the pilot pressure is restrainedfrom dropping correspondingly, and hence the required pilot pressure canbe maintained. Consequently, the air supply valve connected to the sievebed on the air exhaust side (the side of being regenerated) andconfigured to be closed normally can be prevented from opening andthereby causing exhaust air in the sieve bed to flow reversely in theair supply flow channel 5 and flow into the sieve bed on the side inwhich the oxygen at a high concentration is generated. In FIG. 3,vertical dot lines indicate timing of turning ON and OFF of adistribution of power to the electromagnetic pilot valves 20 of therespective air supply valves 7 a, 7 b by the control unit 60, that is,timing of switching of the first valve opening-and-closing pattern andthe second valve opening-and-closing pattern alternately by the controlunit 60.

The configuration of an air pressure circuit including the pilot checkvalve 40 in the oxygen generating portion 2 will be described further indetail. The air pressure circuit of the oxygen generating portion 2 isformed by a valve assembly formed by the first and second air supplyvalves 7 a, 7 b and the first and second exhaust valves 8 a, 8 b mountedon a single manifold base 30 as illustrated in FIG. 1, FIG. 4A to FIG.5. In other words, the manifold base 30 is integrally molded in asubstantially rectangular parallelepiped, and is mounted in a state inwhich the respective air supply valves 7 a, 7 b and the respectiveexhaust valves 8 a, 8 b are adjacent to each other in a two by twopattern on the plane thereof.

The manifold base 30 includes an air supply port P to which the mainflow channel 5 c of the air supply flow channel 5 on the compressor 3side is connected on the plane, and the main flow channel 5 c isbranched in the interior thereof into the first branch flow channel 5 aand the second blanch flow channel 5 b. A front surface of the manifoldbase 30 is provided with a first output port A and a second output portB to which the first and second sieve beds 4A, 4B are connected, and aside surface of the manifold base 30 is provided with an air exhaustport E for discharging exhaust air from the respective exhaust flowchannels 6 a, 6 b formed in the interior thereof to the atmosphere. Inthe interior of the manifold base 30, the pilot flow channel 9 isbranched from the second branch flow channel 5 b.

As illustrated in FIG. 5, first air supply side openings 31 a, 31 b incommunication with the air supply port P and connected respectively tothe first ports 14 a of the first and second air supply valves 7 a, 7 b,second air supply side openings 32 a, 32 b in communication respectivelywith the first and second output ports A, B, and connected respectivelyto the second ports 14 b of these valves, third air supply side openings33 a, 33 b in communication with the pilot flow channel 9, and connectedrespectively to the third ports 14 c of these valves, and fourth airsupply side openings 34 a, 34 b in communication respectively with firstand second pilot exhaust port Ep1, Ep2 formed adjacent to the outputports A, B respectively, and connected respectively to the fourth ports14 d of these valves are disposed respectively in a concentric patternon a plane of the manifold base 30.

In addition, first air exhaust side openings 35 a, 35 b in communicationrespectively with the first and second output ports A, B, and connectedrespectively to the first ports 14 a of the first and second exhaustvalves 8 a, 8 b, second air exhaust side openings 36 a, 36 b incommunication with the air exhaust port E, and connected respectively tothe second ports 14 b of these valves, third air exhaust side openings37 a, 37 b in communication with the pilot flow channel 9, and connectedrespectively to the third ports 14 c of these valves, and fourth airexhaust side openings 38 a, 38 b in communication respectively with thefirst and second pilot exhaust port Ep1, Ep2, and connected respectivelyto the fourth ports 14 d of these valves are disposed respectively in aconcentric pattern on the same plane.

The manifold base 30 is provided with a check valve mounting hole 39 afor inserting the pilot check valve 40 from the outside into theinterior thereof for being mounting in the pilot flow channel 9 so as tobe opened adjacent to the air exhaust port E. As illustrated in FIG. 6,in the manifold base 30, the pilot flow channel 9 is formed by aprimary-side flow channel hole 9 a on the upstream side and asecondary-side flow channel hole 9 b on the downstream side with thecheck valve 40 interposed therebetween. The primary-side flow channelhole 9 a is provided on a side wall biased to the opening of the checkvalve mounting hole 39 a and communicates with the second branch flowchannel 5 b, and the secondary-side flow channel hole 9 b is opened on abottom portion of the check valve mounting hole 39 a in the inner sideand communicates with the electromagnetic pilot valves 20 of therespective valves 7 a, 7 b, 8 a, 8 b via the third air supply sideopenings 33 a, 33 b and the third air exhaust side openings 37 a, 37 b.The primary-side flow channel hole 9 a and the secondary-side flowchannel hole 9 b are formed to have a diameter smaller than the checkvalve mounting hole 39 a, and a shouldered portion 39 b at a boundarybetween the check valve mounting hole 39 a and the secondary-side flowchannel hole 9 b serves as a positioning and stopper of the pilot checkvalve 40 described below in detail.

The pilot check valve 40 is configured to prevent the pilot air fromflowing from the secondary-side flow channel hole 9 b to theprimary-side flow channel hole 9 a reversely to maintain the pilotpressure on the downstream side as illustrated in FIG. 6 and FIG. 7, andincludes a hollow outer cylinder 41 which is to be fitted into the checkvalve mounting hole 39 a and corresponds to an exterior of the checkvalve 40, a hollow core cylinder 42 which is fitted into the outercylinder 41 and forms a flow channel of the pilot air, a check valvemain body 43 arranged in the interior of the same outer cylinder 41, anair filter 44 arranged in the interior of the core cylinder 42, and asealing cap 45 configured to hermetically close the check valve mountinghole 39 a.

The outer cylinder 41 is provided with a first opening 41 a at a firstend in the axial direction thereof, and a second opening 41 b at asecond end on the opposite side, and is fitted into the check valvemounting hole 39 a with the first opening 41 a positioned on the innerside therein. At that time, the second opening 41 b is closed by thesealing cap 45 in a state in which the first end is in abutment with theshouldered portion 39 b, and the first opening 41 a is in communicationwith the secondary-side flow channel hole 9 b. A plurality of first airintroducing holes 41 c for introducing the pilot air into the checkvalve 40 are provided in the circumferential direction on a side wall ofthe outer cylinder 41 at a position corresponding to the primary-sideflow channel hole 9 a in the axial direction. In addition, an annularseal member S1 configured to hermetically seal with respect to the sidewall of the check valve mounting hole 39 a is mounted on an outerperiphery biased to the first end with respect to the first airintroducing holes 41 c. The outer cylinder 41 is provided with ashouldered portion 41 d on an inner surface thereof in the axialdirection at a substantially center thereof, and is formed so as to bedecreased in inner diameter from the second end side to the first endside. The shouldered portion 41 d serves as positioning and a stopper ofthe core cylinder 42 described below in detail.

The core cylinder 42 includes a shaft-shaped valve mounting portion 42 ahaving the check valve main body 43 mounted on the outer peripherythereof, a flow channel forming portion 42 b forming a flow channel ofthe pilot air, and a cylindrical portion 42 c for mounting the airfilter 44 in the interior thereof arranged in this order from the firstend side to the second end side on the opposite side thereof in theaxial direction and integrally molded, and is fitted into the outercylinder 41 from the second opening 41 b thereof with the valve mountingportion 42 a on the first end side positioned on the inner side. Agroove 42 d is formed on the outer periphery of the valve mountingportion 42 a, and the check valve main body 43 is mounted in the groove42 d.

The flow channel forming portion 42 b has a diameter larger than thevalve mounting portion 42 a, and is formed into a hollow cylindricalshape opening on the second end side, and includes a plurality of airderiving holes 42 e arranged in the circumferential direction andconfigured to derive the pilot air flowing into the interior thereoffrom the second end side to a portion between the outer periphery of thecore cylinder 42 and the inner periphery of the outer cylinder 41.

The cylindrical portion 42 c has a diameter larger than that of the flowchannel forming portion 42 b, is formed into a hollow cylinder openingat both ends in the axial direction, and has an outer diametersubstantially the same as an inner diameter of the outer cylinder 41.The first end side thereof communicates with the flow channel formingportion 42 b, and a plurality of second air introducing holes 42 f forintroducing the pilot air into the core cylinder 42 are provided on aside wall in the circumferential direction at positions corresponding tothe first air introducing holes 41 c. The cylindrical portion 42 c is inabutment with the shouldered portion 41 d of the outer cylinder 41 atthe end on the first end side thereof and is closed at the second endthereof by the sealing cap 45 in the state of being mounted in the outercylinder 41. In addition, a seal member S2 configured to hermeticallyseal against the inner wall of the outer cylinder 41 is mounted on anouter periphery of the cylindrical portion 42 c at a position biased tothe first end with respect to the second air introducing holes 42 f.

In addition, the check valve main body 43 includes an annular baseportion 43 a extending in parallel to the axis and fitted into thegroove 42 d of the valve mounting portion 42 a as illustrated in FIG. 6,and an annular lip portion 43 b provided so as to be inclined from theouter periphery of the base portion 43 a toward the first opening 41 aof the outer cylinder 41, and is integrally molded of elastic materialsuch as rubber. In other words, the check valve main body 43 is formedof a lip seal having an annular shape and formed into a substantiallyV-shape opening toward the first opening 41 a in cross section, and adistal end of the lip portion 43 b is in abutment with the inner surfaceof the outer cylinder 41 in a state in which the core cylinder 42 ismounted in the interior of the outer cylinder 41. Accordingly, withrespect to the flow of the pilot air from the primary-side flow channelhole 9 a side, the lip portion 43 b falls over to form a flow channelwith respect to the inner surface of the outer cylinder 41, therebyallowing the flow toward the secondary-side flow channel hole 9 b, andwith respect to the flow from the secondary-side flow channel hole 9 bside, the lip portion 43 b rises up and hence the distal end thereof ispressed against the inner surface of the outer cylinder 41 therebyblocking the flow channel, and hence the flow toward the primary-sideflow channel hole 9 a is prevented.

The air filter 44 is formed into a cylindrical shape havingsubstantially the same diameter and the axial length as the shape of aflow channel chamber 42 g in the cylindrical portion 42 c so as to bemountable by being inserted into the flow channel chamber 42 g from thesecond end side of the cylindrical portion 42 c. The air filter 44covers the entire part of the second air introducing holes 42 f in thestate of being mounted in the flow channel chamber 42 g.

The sealing cap 45 is formed into a solid disc shape in the axialdirection, and a seal member S3 configured to hermetically seal withrespect to the inner surface of the outer cylinder 41 is mounted on theouter periphery thereof. At this time, the sealing cap 45 may beconfigured to be demountably mountable with respect to the check valvemounting hole 39 a, so that the maintenance of the check valve 40 can beperformed as needed.

In the pilot flow channel 9 provided with the pilot check valve 40 asdescribed above, the pilot air from the primary-side flow channel hole 9a is introduced into the cylindrical portion 42 c through the first andsecond air introducing holes 41 c, 42 f opening respectively on the sidewall of the outer cylinder 41 and the side wall of the cylindricalportion 42 c of the core cylinder 42. Then, the pilot air is filtered bythe air filter 44 mounted in the cylindrical portion 42 c, then flowsinto the flow channel forming portion 42 b of the core cylinder 42, isderived out to a portion between the outer surface of the core cylinder42 and the inner surface of the outer cylinder 41 through the airderiving holes 42 e, and is guided to the first opening 41 a of theouter cylinder 41 communicating with the secondary-side flow channelhole 9 b through the periphery of the check valve main body 43. Incontrast, the flow from the secondary-side flow channel hole 9 b towardthe primary-side flow channel hole 9 a is prevented by the check valvemain body 43.

Therefore, even though air supply pressure in the air supply flowchannel 5 drops, the pilot pressure of the pilot flow channel 9 can bemaintained. In addition, the pilot check valve 40 can be mounted easilyin the pilot flow channel 9 formed in the interior of the manifold base30 from the outside of the manifold base 30.

FIG. 8 illustrates a modification 40A of the pilot check valve. Here, inorder to avoid overlapping of description, portions having differentconfigurations from the pilot check valve 40 illustrated in FIG. 6 aremainly described, and description of the parts having the sameconfigurations is omitted by denoting with the same reference numeralsas those illustrated in FIG. 6.

In the pilot check valve 40A of this modification, a core cylinder 46has a configuration in which the valve mounting portion 42 a and theflow channel forming portion 42 b are omitted from the core cylinder 42of the check valve 40, that is, has the same form as the cylindricalportion 42 c. The core cylinder 46 includes an air deriving hole 46 aconfigured to derive the pilot air from the interior of the corecylinder 46 into the outer cylinder 41, and a valve seat 46 b formed inthe periphery of the air deriving hole 46 a so as to surround the airderiving hole 46 a on an end surface of the outer cylinder 41 located onthe first opening 41 a side.

A check valve main body 47 formed of a poppet valve is provided in theouter cylinder 41 adjacent to the core cylinder 46 in the axialdirection. The check valve main body 47 is disposed coaxially on thefirst opening 41 a side of the core cylinder 46, and is inserted intothe outer cylinder 41 so as to be capable of moving reciprocally alongthe axis, and the first end on the first opening side and the second endon a side opposite thereto (the core cylinder 46 side) in the axialdirection form first and second pressure receiving surfaces 47 a, 47 b,respectively. An annular sealing rib 47 c configured to be brought intoand out of contact with the valve seat 46 b in association with thereciprocal motion of the check valve main body 47 is provided at aposition on the second pressure receiving surface 47 b on the corecylinder 46 side so as to project therefrom. The check valve main body47 includes a spring seat 47 d on the outer periphery thereof, is biasedtoward the core cylinder 46 by a coil spring 48 as a biasing memberprovided between the spring seat 47 d and the shouldered portion 39 b ofthe check valve mounting hole 39 a, so that the sealing rib 47 c isbrought into abutment with the valve seat 46 b by a biasing forcethereof.

In this configuration, with respect to the flow of the pilot air fromthe primary-side flow channel hole 9 a side, the check valve main body47 is slid by the pressure applied to the second pressure receivingsurface 47 b of the check valve main body 47 toward the first openingside along the axial direction and the sealing rib 47 c moves away fromthe valve seat 46 b, so that the pilot air is allowed to flow from theair deriving hole 46 a of the core cylinder 46 toward the first openingthrough a gap between an outer peripheral surface of the check valvemain body 47 and an inner peripheral surface of the outer cylinder 41.In contrast, with respect to the flow from the secondary-side flowchannel hole 9 b side, the check valve main body 47 is slid by thepressure applied to the first pressure receiving surface 47 a toward thecore cylinder 46 side along the axial direction, and the sealing rib 47c is pressed against the valve seat 46 b, whereby the flow channel isblocked and the flow toward the primary-side flow channel hole 9 a isprevented.

FIG. 9 illustrates another embodiment of the oxygen concentrator 1 ofthe present invention. Here, in order to avoid overlapping ofdescription, portions having different configurations from the oxygenconcentrator 1 illustrated in FIG. 1 are mainly described, anddescription of the parts having the same configurations is omitted bydenoting with the same reference numerals as those illustrated in FIG.1.

In this embodiment, the main flow channel 5 c of the air supply flowchannel 5 is branched into the first branch flow channel 5 a and thesecond branch flow channel 5 b on the upstream side of the manifold base30, and the manifold base 30 is provided with a first air supply port Paand a second air supply port Pb for connecting the respective branchflow channels 5 a, 5 b.

A first pilot flow channel 19 configured to supply the pilot air to theelectromagnetic pilot valves 20 of the first air supply valve 7 a andthe first exhaust valve 8 a is branched from the first branch flowchannel 5 a in the manifold base 30, and a first pilot check valve 40 aconfigured to prevent the pilot air from flowing reversely is providedat a position in the pilot flow channel 19 on the upstream side of theair supply valve 7 a.

A second pilot flow channel 29 configured to supply the pilot air to theelectromagnetic pilot valves 20 of the first air supply valve 7 b andthe second exhaust valve 8 b is branched from the first branch flowchannel 5 b in the manifold base 30, and a second pilot check valve 40 bconfigured to prevent the pilot air from flowing reversely is providedat a position in the pilot flow channel 29 on the upstream side of thefirst air supply valve 7 a.

Specifically, in the manifold base 30, the first and second pilot flowchannels 19, 29 include primary-side flow channel holes 19 a, 29 a onthe upstream side and secondary-side flow channel holes 19 b, 29 b onthe downstream side with the check valves 40 a, 40 b interposedtherebetween, respectively, as those illustrated in FIG. 6 and FIG. 8,and these check valves 40 a, 40 b allow the pilot air to flow from theprimary-side flow channel holes 19 a, 29 a to the secondary-side flowchannel holes 19 b, 29 b and block the flow from the secondary-side flowchannel holes 19 b, 29 b to the primary-side flow channel holes 19 a, 29a.

Accordingly, as illustrated in FIG. 3, the pilot pressure is preventedfrom dropping in association with dropping of the air supply pressureimmediately after having switched between the “first valveopening-and-closing pattern” and the “second valve opening-and-closingpattern”, and the required pilot pressure can be maintained.

Although the embodiments of the oxygen concentrator of the presentinvention have been described thus far, the present invention is notlimited to the above-described respective embodiments, and variousmodifications of design are possible without departing the gist of thepresent invention. For example, in the embodiment illustrated in FIG. 1,the pilot flow channel 9 is branched from the second branch flow channel5 b. However, the pilot flow channel 9 may be branched from the firstbranch flow channel 5 a or, branched from the both branch flow channels5 a, 5 b respectively in the same manner as the embodiment of FIG. 9. Inaddition, in the embodiment of FIG. 1, in the same manner as theembodiment of FIG. 9, the main flow channel 5 c may be branched into thefirst and second branch flow channels 5 a, 5 b on the upstream side ofthe manifold base 30. In addition, in the embodiments illustrated inFIG. 1 and FIG. 9, the pilot flow channels 9, 19, 29 may be branched notfrom the branch flow channels 5 a, 5 b, but from the main flow channel 5c.

REFERENCE SIGNS LIST

-   1: oxygen concentrator-   2: oxygen generating portion-   3: compressor (compressed air supply source)-   4A: first sieve bed-   4B: second sieve bed-   5: air supply flow channel-   5 a: first branch flow channel-   5 b: second branch flow channel-   5 c: main flow channel-   6: exhaust flow channel-   7 a: first air supply valve-   7 b: second air supply valve-   8 a: first exhaust valve-   8 b: second exhaust valve-   9. 19, 29: pilot flow channel-   10: diaphragm valve-   20: electromagnetic pilot valve-   30: manifold base-   40, 40A, 40 a, 40 b: pilot check valve (check valve)

The invention claimed is:
 1. An oxygen concentrator comprising: acompressed air supply source for outputting compressed air; first andsecond sieve beds including an absorbing material configured toselectively adsorb nitrogen from air under increased pressure anddischarge the adsorbed nitrogen under reduced pressure integratedtherein and configured to generate oxygen at a high concentration byseparating nitrogen from the compressed air; an air supply flow channelsupplying the compressed air from the compressed air supply source tothe respective sieve beds respectively; an exhaust flow channeldischarging exhaust air in each of the sieve beds to the atmosphererespectively, the air supply flow channel including a main flow channelconnected to the compressed air supply source and first and secondbranch flow channels branched from the main flow channel and connectedto the first and second sieve beds, first and second air supply valvesprovided respectively in the first and second branch flow channels andconfigured to communicate the compressed air supply source with thefirst and second sieve beds alternately; and an exhaust valve providedin the exhaust flow channel and configured to communicate the firstsieve bed with the atmosphere when the first air supply valve is closed,and communicate the second sieve bed with the atmosphere when the secondair supply valve is closed, wherein the air supply valves each include adiaphragm valve as a main valve and an electromagnetic pilot valvedriving the main valve in a direction of closing the branch flow channelby pilot air, a pilot flow channel supplying the pilot air to theelectromagnetic pilot valves is branched from a position on the upstreamside of the air supply valves in the air supply flow channel, and acheck valve preventing the pilot air from flowing reversely is providedin the pilot flow channel, wherein the first and second air supplyvalves and the exhaust valve are mounted on a single manifold base, themanifold base includes the air supply flow channel, the pilot flowchannel branched from the air supply flow channel, the exhaust flowchannel, and the check valve mounted therein, wherein the manifold baseis provided with a check valve mounting hole for inserting and mountingthe check valve from the outside formed therein, the pilot flow channelis formed by a primary-side flow channel hole extending from a side wallof the check valve mounting hole to the air supply flow channel and asecondary-side flow channel hole extending from an inner portion of thecheck valve mounting hole to the electromagnetic pilot valve, andwherein the check valve includes a hollow outer cylinder provided with afirst opening configured to communicate with the secondary-side flowchannel hole at an end in an axial direction, and is fitted in the checkvalve mounting hole with the first opening on the inner side, and acheck valve main body configured to prevent pilot air from a hollow corecylinder disposed in the outer cylinder and the secondary-side flowchannel hole from flowing reversely, the pilot air from the primary-sideflow channel hole is introduced into the core cylinder through first andsecond air introducing holes formed on side walls of the outer cylinderand the core cylinder respectively, is derived out from the interior ofthe core cylinder through an air deriving hole provided on the corecylinder, and is guided to the first opening through the periphery ofthe check valve main body.
 2. The oxygen concentrator according to claim1, wherein one pilot flow channel supplying pilot air to both of theelectromagnetic pilot valves of the first and second air supply valvesis branched from the air supply flow channel.
 3. The oxygen concentratoraccording to claim 1, wherein first and second pilot flow channelssupplying pilot air to the respective electromagnetic pilot valves ofthe first and second air supply valves are branched respectively fromthe air supply flow channel.
 4. The oxygen concentrator according toclaim 1, wherein the check valve main body is an annular lip seal havinga cross sectional shape of a V-shape opening on the first opening sideof the outer cylinder.
 5. The oxygen concentrator according to claim 2,wherein the check valve main body is an annular lip seal having a crosssectional shape of a V-shape opening on the first opening side of theouter cylinder.
 6. The oxygen concentrator according to claim 3, whereinthe check valve main body is an annular lip seal having a crosssectional shape of a V-shape opening on the first opening side of theouter cylinder.
 7. The oxygen concentrator according to claim 1, whereinthe air deriving hole is formed in an end surface of the core cylinderlocated at a position on the first opening side of the outer cylinder sothat a poppet valve as the check valve main body provided in the outercylinder comes into and out of contact with a valve seat formed so as tosurround the air deriving hole.
 8. The oxygen concentrator according toclaim 2, wherein the air deriving hole is formed in an end surface ofthe core cylinder located at a position on the first opening side of theouter cylinder so that a poppet valve as the check valve main bodyprovided in the outer cylinder comes into and out of contact with avalve seat formed so as to surround the air deriving hole.
 9. The oxygenconcentrator according to claim 3, wherein the air deriving hole isformed in an end surface of the core cylinder located at a position onthe first opening side of the outer cylinder so that a poppet valve asthe check valve main body provided in the outer cylinder comes into andout of contact with a valve seat formed so as to surround the airderiving hole.
 10. The oxygen concentrator according to claim 1, whereinan air filter is mounted in the core cylinder so as to cover the secondair introducing holes.
 11. The oxygen concentrator according to claim 2,wherein an air filter is mounted in the core cylinder so as to cover thesecond air introducing holes.
 12. The oxygen concentrator according toclaim 3, wherein an air filter is mounted in the core cylinder so as tocover the second air introducing holes.
 13. The oxygen concentratoraccording to claim 1, wherein a second opening is formed at the otherend, which is on a side opposite to the first opening of the outercylinder so that the core cylinder can be fit in the outer cylinderthrough the second opening, and the check valve mounting hole ishermetically closed by a sealing cap configured to close the secondopening of the outer cylinder.
 14. The oxygen concentrator according toclaim 2, wherein a second opening is formed at the other end, which ison a side opposite to the first opening of the outer cylinder so thatthe core cylinder can be fit in the outer cylinder through the secondopening, and the check valve mounting hole is hermetically closed by asealing cap configured to close the second opening of the outercylinder.
 15. The oxygen concentrator according to claim 3, wherein asecond opening is formed at the other end, which is on a side oppositeto the first opening of the outer cylinder so that the core cylinder canbe fit in the outer cylinder through the second opening, and the checkvalve mounting hole is hermetically closed by a sealing cap configuredto close the second opening of the outer cylinder.